It has been known for many years that naphthalene sulfonic acid can be condensed with formaldehyde to form useful reaction products. See, e.g., Frohmader, U.S. Pat. No. 2,529,602, and Johnson, U.S. Pat. No. 3,277,162. Geo Specialty Chemicals, Inc. of Cleveland, Ohio, the assignee of the present application, markets a line of sulfonated naphthalene formaldehyde condensate products under the LOMAR® mark that are useful in a variety of applications, including as dispersants and/or plasticizers in the manufacture of aqueous cementitious products (e.g., concrete and gypsum), and in the oil field, ceramics and polymerization industries.
The naphthalene used in the manufacture of prior art sulfonated naphthalene formaldehyde condensate products is relatively pure, typically comprising greater than 96% naphthalene by weight. Such naphthalene will have a melting point of at least about 78° C., and more preferably at least about 78.5° C.
Naphthalene is principally derived from the fractional distillation and recrystallization of coal tar, which is a by-product obtained during the production of coke used in the steel industry. The “middle fraction” obtained during the fractional distillation of coal tar includes a mixture of “light oils” that boil within a range of from about 200° C. and 250° C. Because the middle fraction is relatively rich in naphthalene (i.e., typically containing from about 50% to about 75% naphthalene by weight), it is sometimes referred to as naphthalene oil or dilute naphthalene oil. In addition to naphthalene, naphthalene oil comprises a complex mixture of hundreds of compounds, primarily multi-ringed polynuclear aromatic hydrocarbons. Naphthalene oil must be further refined and processed in order to separate the naphthalene from these other compounds. Because the refinement of naphthalene oil is relatively expensive, a substantial volume of naphthalene oil is burned to generate heat.